CC Nerd-The Case of the Elusive Mirage

Tales are often told of an exhausted travel who has lost their way in the desert, and are drawn astray by the the sight of a lush oasis. But as they draw close, their salvation vanishes only to reappear on the distant horizon. This optical tormentor continues to lead the hapless travelers further and further off course, until they collapse from sheer exhaustion. Such is the fallacy of the video laryngoscope. Or at least so it appears…

Published in JAMA, Lascarrou et al examined the efficacy of video laryngoscopy when compared to a traditional direct approach in patients requiring endotracheal intubation in 7 ICUs across France. The MACMAN trial randomized patients to either a first attempt using the standard geometry McGrath Mac Video laryngoscope vs a traditional Macintosh blade. Randomization was stratified by center and the experience level of the intubator performing the procedure. The authors utilized a strict protocol in an attempt to control for variations in practice that could potentially bias the results (variations in pre-oxygenations techniques, induction medication, etc.). An intubation attempt was defined from the time the laryngoscope blade was inserted into the patient’s oral cavity until the blade was removed. Successful intubation required confirmation using a waveform end-tidal CO2 monitor.

371 patients were randomized and included in the intention to treat analysis. The authors found no difference in their primary outcome, the rate of first pass success, between the two groups. 67.7% of the patients randomized to the video laryngoscopy group were intubated successfully on the first attempt compared to 70.3% of the patients in the direct laryngoscopy group. Nor did they find a difference in the number or duration of intubation attempts or the frequency of difficult intubation. The authors did note a concerning statistically significant increase in the number of severe life-threatening complications that occurred in the patients who underwent intubation using the video laryngoscope (9.5% vs 2.8%).

In addition, this study highlights the fallacy of video laryngoscopy. I am sure we have all felt the utter frustration of having a beautiful view of the vocal cords displayed on our high resolution screen only to watch our tube slip just below the interarytenoid notch over and over again. Lascarrou et al kindly demonstrated that we are not alone in this frustration. In fact, this shared vexation is quite commonplace. The video laryngoscope far outperformed its traditional brethren when it came to visualization of the vocal cords. Cormack-Lehane grade 1 views were achieved in 75.6% of the patient in the video laryngoscope group. This optimal view was only achieved in 52.5% of the patients who underwent direct laryngoscope. And while the rate of first pass failure was clinically identical between the two groups, how each group failed differed significantly. The primary reason for failure in patients who were randomized to receive direct laryngoscope was failure to visualize the glottis (70.6%). In contrast to the video laryngoscope group, the primary reason of failure was inability to pass the tube (70.7%). The study protocol prohibited intubators from utilizing an intubating stylet during their first attempt. This may have contributed to the failure rate when using the video laryngoscope and likely explains the increased use of the gum elastic bougie on first attempt (12% vs 5.5%). This is not a novel phenomenon, multiple studies have demonstrated while video laryngoscopy enhances glottic visualization, it does not improve clinically important outcomes (2,3,4,5). In fact, Gu et al found that a more limited view when using a hyperangulated video laryngoscope led to improved rates of success when compared to what is considered the ideal visualization of the glottic structures. Unfortunately, Lascarrou et al did not decipher the types of patients in which each of these respective modalities fail. Did these modalities fail in the same patients or does one device suffer where another may succeed? Perhaps we should tailor our blade selection to the specific anatomical and physiological challenges presented by the patient in front of us.

Despite my old fashioned love of the traditional direct laryngoscope, this study underestimates the true utility of a standard geometry video laryngoscope as it functions as both a direct and indirect laryngoscope in parallel rather in series. I imagine that if intubators were allowed to transition from an indirect view to a direct view of the glottis and vice versa when either failed, the video laryngoscope group would have appeared far more favorable. Though to be fair this is nothing more than conjecture.

Though this paper certainly has its limitations, it does highlight a number of key points. First, neither of these methods are perfect. When employed by inexperienced hands, both direct and video laryngoscopy will fail frequently. More importantly, this data set should remind us that when it comes to the airway, experience reigns supreme. The expert intubators far outperformed their less experienced peers (91.7% vs 64.6%), independent of the type of blade they used during the intubation. Video laryngoscopy does not simplify airway management, rather it changes the perspective. Reminding us while vivid and often gruesome images of the airway may appear advantageous, glottic visualization does not necessarily translate into successful intubation. Like the weary traveler, chasing the ever retreating mirage, at times its path does not always lead to salvation.

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I wonder what the differences would be providers who do not get the hours often enough to be highly proficient in intubation (such as Military medics) would be.
Great post!

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1 year ago

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Grant Price

Hi my name is Grant Price from Edinburgh, Scotland. This study adds greatly to the debate. Of course those who take it as an article of faith that VL outperforms DL with a Macintosh blade wont be convinced and find holes, especially if their VL of choice is not the Macgrath device used in this study. There are studies demonstrating the very high reliabilty of tracheal intubation with a standard Macintosh laryngoscope in trained hands. The 2 below show intubation success rates of near 100% with no more than 2 intubation attempts. https://www.ncbi.nlm.nih.gov/pubmed/25038154 https://www.ncbi.nlm.nih.gov/pubmed/22315326 So in my view rather than promoting VL to displace DL from being 1st line, we need to define when VL should be used once DL fails and what works best for particular anatomical problems e.g hyperangulated blade and how best to actually deliver the tracheal tube reliably, rather than being enamoured by pretty pictures of the larynx. Regarding your point about the use of a Macintosh geometry blade as part of a VL device, well the Macgrath is marketed as such, and fans of it use your argument to promote its use. Sadly when studied objectively it doesnt quite live up to that promise either.… Read more »

Wonderful Grant, Thank you so much for this thoughtful commentary. I agree 100%. I think the most important point that os often overlooked in this debate is not which is better DL or VL, as most of the data demonstrates that they are equivalent in the hands of an expert. But rather that VL is not a replacement for skill and planning. That a VL device will somehow simplify all airways is common misconception despite having been demonstrated in the literature time and time again to not be true.

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1 year ago

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Dave E

About 8 years ago, I was attending an annual EM conference in the Mountain West. One of the speakers – I believe from Brigham and Betterthan U. (or something like that) – was on stage stating that VL was “standard of care” over DL. I took issue with this for several reasons delineated below. I feel slightly smug that there is still some debate.

First, I’ll echo that experience does reign supreme and I wonder when I read these studies how the failure rates could be so high (I’ll certainly struggle with my next tube for saying this – Karma!)

Second, neither work very well underwater and a second set of hands with suction, assist, etc. works better than fiber optics in this case. Plan (AHEAD OF TIME) accordingly. .

A better tool IMHO is consideration and anticipation of the specific airway problem before induction and having your best guess at a solution at hand and ready – which may be help rather than a fancy device.

I have a hard time taking a study where first pass success in each group is only around 70% and applying that to my real world experience in the ED. That type of first pass success rate seriously reminds me of interns/junior residents getting their first few dozen tubes. I do fully agree that the common issue with a glidescope, perhaps less significantly with other non-hyper-angulated video scopes, is seeing the cords but not being able to pass the tube. However, this I have found is easily rectified in the great great majority of cases with teaching the laryngoscopist proper technique with this instrument, which is markedly different than standard direct laryngoscopy– (1) Use the rigid curved stylet (with glide scope specifically) (2) Hold the tube/stylet at its most distal end, allowing you better freedom to rotate the tip upwards (3) Instead of placing the cords “zoomed in” in the middle of your video screen, place them “zoomed out” in the upper left hand corner. This gives you an earlier and wider view of the tip of your tube, allowing you to move it anteriorly if needed. (4) If needed, “trace” the tip of your tube down the blade of… Read more »

Now, *knock on wood*, I’ve had only 1 first pass failure with a glide scope in the past 5 years– when blood splashed on the lens and occluded the view– and was immediately saved with DL. Excluding equipment failure (light bulbs..) I’ve had only 1 DL first pass failure in the same time period (surprisingly large tongue/tight mouth/anterior structure… should have anticipated better frankly) which was easily saved with glidescope. I do think they are complimentary techniques, and I alternate which I use to keep proficient with both, unless I predict one will be vastly superior in a specific patient.